In the quest for the most rigid Ender 3 Pro in the land, I stumbled across this model: https://www.thingiverse.com/thing:3343666 from mlynch002 and made some changes.

Changes:

• Repaired and remeshed model
• Resized Holes to M5
• Added flat version without cable cutout
• Added Left, Right models
• Added Full bracket for 4040 extrusions (Ender 3 Pro)
• Added Full bracket for 2020 extrusions (Ender 3)

Hardware Needed:

• M5 Bolts 8-12mm (14 for Full Bracket, 7 for Half Bracket)
• M5 T-Nuts (14 for Full Bracket, 7 for Half Bracket)

Print Settings:

• Layer Height: 0.2mm
• Line Width: 0.6mm
• Brim: Recommended (thin walls that make up the side of the Y-Axis support like to peel)
• Infill: your choice, I did 100%
• Wall Count: 3-4
• Support: Yes, for models with cable cutout (otherwise, no)
• Y_Bracket_Full_without_Cable took 4 hours at 60mm/s (44 total grams)
• Filament: 3D Fuel Pro PLA - Midnight Black

Installation Notes:

• See pictures for more details
• After installing the appropriate nuts and bolts, slide bracket onto the Y-Axis extrusion and slide until it is snug against the horizontal extrusion (Might be a tight fit, depending on your printer tolerances)
• All versions of the bracket should fit on the front or rear of the center extrusion
• The models labeled “RIGHT” should fit with the stock electronics case on the Ender 3 family of printers
• I am using dual "FULL" brackets since I moved my electronics and screen to an external enclosure
• .obj file included if you want to make any changes